Christopher Dorner was born in New York, and his family moved to Los Angeles County when he was young.
He later claimed to have been the only African-American student at his primary school and told of how he suffered racist abuse at school.
He graduated from Southern Utah University in 2001 with degrees in political science and in psychology.
Dorner served as a US Navy reservist from July 2002 until 1 February, when he was honourably discharged – days before he allegedly began his shooting spree.
Over the years he had become a skilled marksman, completing a large number of weapons training courses. He joined the Los Angeles Police Department (LAPD) in 2005, completing its training programme the following year.
In November 2006, he was deployed, as a navy reservist, to Bahrain aboard a patrol craft in the Gulf. The group provided security for military operations in the Gulf.
He returned to work for LAPD but, in September 2008, his contract was terminated after he filed a report concerning the conduct of fellow officer, Teresa Evans.
He claimed she used excessive force when dealing with a suspect, who was handcuffed and lying on the ground.
An internal review board claimed Dorner had lied in his report, despite the corroborating statements of the kicking victim and his father.
Dorner cited his sacking and his sworn testimony that such excessive force did occur, in his online “manifesto” this month, as his reason for planning unspecified violence.
The document included a list of people he wanted revenge on for being sacked. It included a number of police personnel.
The LAPD last week announced it would reopen the disciplinary proceedings that led to Dorner being dismissed.